Dilemma: I have cooking oil that's gone rancid. Do I pour it into the compost bin or send it down the sink drain?

Of course I'll: Pour it into the compost bin. It's food, after all.

Trade-off: As smelly and messy as the green bin is now, the oil is just going to make it worse.

Then I'll: Pour the oil down the sink.

Trade-off: I don't want to risk clogging the pipes.

Experts say: The East Bay Municipal Utility District sounds the alarm about this one on its website: "Cooking oil and grease poured down drains can build up in pipes causing backups at home, into streets and the storm drain system. ... Overflows can pose health and environmental hazards, polluting local creeks and San Francisco Bay." That's even if you use hot water, detergents or garbage disposals. For its part, the San Francisco Public Utilities Commission estimates that unclogging pipes stopped up by used cooking oils costs the city more than $3.5 million each year.

But pouring the oil into the compost bin isn't necessarily the answer either. Darby Hoover, senior resource specialist for the Natural Resources Defense Council, says, "In home compost bins, cooking oils in quantity can attract animals." Oils also make it hard for oxygen to get through, which means your pile will probably become anaerobic rather than aerobic. She says that while anaerobic home compost will still break down eventually, "it takes longer and smells worse while it's happening - you know it's anaerobic if it's slimy and smells."

Verdict: Never pour the oil down the sink. The best course of action is to check out one of the local grease recycling programs like SFGreasecycle, which tries to turn residential fats, oil and grease into biofuel (bit.ly/oEhM0Q) and EBMUD's residential cooking oil and grease drop-off locations (bit.ly/qllznq).

Robert Reed, spokesman for Recology, the company that processes household waste in San Francisco, suggests collecting fat from frying bacon or hamburgers into an empty soup or coffee can. "It wouldn't make sense to make a trip and burn gasoline just to take in a small amount of household cooking oil, but saving it until you have a significant quantity and taking it in when you are going to be in the vicinity of an authorized drop-off would be efficient and allow the oil to be processed into biodiesel," Reed says.

Alternatively, a few Bay Area municipalities, including San Francisco among them, can process small quantities - a tablespoon or three per household - of cooking oil in compost. Hoover recommends mixing the oil with something that will absorb it, like food-soiled paper or leaves, before putting it in the green bin.